public class Text3 {
    // 69.x的平方根
    public int mySqrt(int x) {
        long left = 1, right = x;

        if(x < 1)
            return 0;
        while(left < right){
            long mid = left + (right - left + 1)/2;
            if(mid * mid < x){
                left = mid;
            } else if(mid * mid > x){
                right = mid - 1;
            } else {
                left = mid;
                break;
            }
        }

        return (int)left;
    }
}
